Power semiconductor manufacturing method

Abstract

The invention relates to the technical field of semiconductors, in particular to a power semiconductor manufacturing method, which comprises the following steps of: S100, bonding a pin frame on a DBC (Direct Bonding Copper) board by utilizing ultrasonic energy of an ultrasonic terminal bonding machine; a plurality of pins are arranged on the pin frame; s200, carrying out a push-pull force test on the DBC board; s300, carrying out static electricity removal and purging treatment on the DBC board; s400, mounting a plurality of chips on the DBC board, and bonding metal wires between the DBC board and the chips and between the chips to form electric connection between the DBC board and the chips and electric connection between the chips; s500, performing glue pouring treatment on the chip and the metal wire on the DBC board, and performing curing treatment on the DBC board; and S600, performing rib cutting treatment on the DBC board. By adopting the scheme, the influence of thermal stress generated by high temperature during chip welding on the pin bonding area can be avoided, and the product power pin bonding yield is improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for manufacturing a power semiconductor. Background Art

[0002] In modern electronic manufacturing, the reliability and production efficiency of power semiconductor modules are crucial. These modules usually include multiple power chips, which need to work together through precise electrical connections to ensure the performance and stability of the entire system. Traditional connection methods mainly rely on ultrasonic bonding technology and welding technology, but these methods have some significant problems and challenges in practical applications.

[0003] Ultrasonic bonding technology is a method that uses high-frequency vibration energy to achieve metal-to-metal connections. It applies ultrasonic energy to cause plastic deformation of the metal surface to form a strong metal bond. This method has been widely used in the field of microelectronic packaging, especially when connecting tiny power chips. However, when it comes to power pins with large area and thickness, the efficiency and reliability of ultrasonic bonding are affected. Due to the large size of the power pins, the ultrasonic energy may not be evenly transmitted to the entire contact surface, resulting in incomplete bonding and the appearance of gaps, which reduces the strength and stability of the connection.

[0004] Soldering technology is another commonly used connection method, especially when large-area and thick-section components need to be connected. However, the solder used in the welding process is prone to voids, which not only reduces the mechanical strength of the connection, but also may cause unstable electrical performance. In addition, the complexity of the welding process itself, high cost, and high requirements for operating skills have limited its application in the production of power semiconductor modules.

[0005] The plastic packaged insulated gate bipolar transistor (DPIM IGBT) power module is a high-performance power electronic device widely used in motor drive, renewable energy system and other fields. However, the manufacturing process of these modules is complicated and prone to problems such as cold soldering, DBC board cracking and pin falling off. These problems not only affect the yield of the product, but also increase the production cost. Especially for the power pins, the existing power pin ultrasonic bonding manufacturing process usually welds the power chip on the DBC board first and then bonds the pins. This process causes the DBC board to be thermally stressed and deformed after the power chip is welded. At this time, the electrode pins will be bonded again. The following problems will occur: on the one hand, it is easy to cause uneven force on the DBC board and crack; on the other hand, due to material stress, the metal layer in the power pin area is easy to deform. At this time, the pin bonding is prone to incomplete bonding of the power pin, bonding gaps, easy detachment of the power pin, and low reliability of the encapsulated power module.

[0006] Specifically, during the soldering process of the power chip patch, thermal stress is usually generated, which causes the DCB board to produce the following Figure 2 As shown in the deformation, there will be a certain gap when the deformed DBC board is placed in the bonding fixture, which will cause the following problems: on the one hand, the gap will cause the bonding fixture to lose its airtightness when evacuating the vacuum, making it impossible to stably fix the DBC board. This instability will cause the ultrasonic energy to easily move the DBC board during the bonding process, further causing the DBC board to break and the bonding failure; on the other hand, the gap will cause the DBC board to warp, making the bonded power pins not coplanar with the surface of the DBC board, further causing the ultrasonic bonding friction surface to be non-parallel and uneven, thereby producing a virtual pressure state (this is an undesirable state in the bonding process, which can easily cause the pins to fall off). Ultimately, this situation will lead to bonding failure and affect the production yield of the product.

[0007] Therefore, there is an urgent need to provide a power semiconductor manufacturing method that can avoid the influence of thermal stress generated by high temperature during chip welding on the pin bonding area, thereby improving the bonding yield of the product power pin, avoiding the existence of bonding gaps after pin bonding, which causes the power pin to fall off easily, and making the bonded product show better results in thrust detection and eutectic area comparison, and higher bonding strength, so as to improve the reliability and life of the power module in terminal applications. Summary of the invention

[0008] The present invention provides a power semiconductor manufacturing method, which can avoid the influence of thermal stress generated by high temperature during chip welding on the pin bonding area, thereby improving the bonding yield of the product power pin, avoiding the existence of bonding gaps after the pins are bonded, which causes the power pins to fall off easily, and makes the bonded products show better results in thrust detection and eutectic area comparison, and the bonding strength is higher, so as to improve the reliability and life of the power module in terminal applications.

[0009] In order to achieve the above objectives, this application provides the following technical solutions:

[0010] A method for manufacturing a power semiconductor comprises the following steps:

[0011] S100, bonding a lead frame to a DBC board using ultrasonic energy of an ultrasonic terminal bonding machine; the lead frame is provided with a plurality of leads;

[0012] S200, push and pull force test of DBC board;

[0013] S300, performing static electricity removal and purging treatment on the DBC board;

[0014] S400, mounting a plurality of chips on the DBC board, and bonding metal wires between the DBC board and each chip and between the chips to form electrical connections between the DBC board and the chips and between the chips;

[0015] S500, performing glue filling processing on the chip and metal wire on the DBC board, and performing a curing processing on the DBC board after the glue filling processing;

[0016] S600, perform rib cutting on the DBC board, retain the pins on the lead frame, and cut off the connecting parts on the lead frame.

[0017] The principles and advantages of the present invention are:

[0018] 1. Improve the bonding yield: By placing the pin bonding process before the power chip welding, the influence of the thermal stress generated by the high temperature during chip welding on the pin bonding area is avoided, thereby improving the product power pin bonding yield. This change ensures the integrity of the bonding point and reduces the breakage or damage caused by welding stress. Compared with the prior art, the present invention places the pin bonding process before the power chip welding after adjusting the process, thereby avoiding the influence of the stress generated by chip welding on the power pin bonding area, and can ensure that the DBC board can be firmly fixed on the bonding fixture by vacuuming before bonding, and ensure that the DBC board does not shift during ultrasonic energy vibration, resulting in failure of the bonding pin. At the same time, the friction surfaces of the electrical metal layer of the pin and the DBC board are parallel, ensuring full contact between the electrical metal layer of the pin and the DBC board. During bonding, a larger eutectic surface can be formed between the two, reducing virtual pressure, improving the stability of the power module pin, and not easily falling off due to external factors, thereby improving the reliability of its terminal application. The bonded product shows better results in thrust detection and eutectic area comparison, and has higher bonding strength, which makes the final manufactured power semiconductor module product perform better in terms of electrical performance and reliability, and improves the reliability and life of the power module in terminal applications. The prior art believes that the high temperature during the subsequent chip welding process after pin bonding may cause thermal fatigue or damage to the bonded pins, because the pin bonding material (such as gold wire) is very sensitive to temperature. However, this solution verifies the effectiveness and reliability of this solution through a large number of experiments and tests, avoiding fatigue or damage of the first bonded pins due to the high temperature during the chip welding process, and ensuring that the product meets or even exceeds the original quality standards.

[0019] 2. Ensure connection strength and production quality: Perform push-pull force tests on the bonded DBC boards to ensure that each bonding point has sufficient mechanical strength to withstand various stresses in subsequent processes and use, and to identify and eliminate potential poor bonding problems; perform static electricity removal and purge treatments on the DBC boards after the tensile test to eliminate static electricity accumulation and remove surface impurities, providing a clean, static-free surface for subsequent chip mounting, thereby improving the overall production quality.

[0020] 3. Enhance the durability of the DBC board: Utilize the ultrasonic energy of the ultrasonic terminal bonding machine to bond the lead frame to the DBC board. Use power bonding and precisely adjust the bonding parameters to effectively avoid the DBC board from breaking during the manufacturing process. The integrity of the DBC board is crucial to ensuring the performance of the final product. This improvement improves the overall production yield.

[0021] 4. Improve production efficiency and reduce costs: The method provided by the present invention reduces the time, equipment and raw materials required for the power pin welding process, improves production efficiency and saves costs. At the same time, since the welding steps are reduced, the risk of potential defects such as cold welding caused by welding is also reduced.

[0022] In summary, this solution is adopted to optimize the manufacturing process, and the pin bonding process is placed before the power chip welding, which avoids the influence of thermal stress generated by high temperature during chip welding on the pin bonding area, thereby avoiding the existence of bonding gaps after ultrasonic bonding of the pins, which causes the power pins to fall off easily, thereby improving the product power pin bonding yield, so that the bonded products show better results in thrust detection and eutectic area comparison, and have higher bonding strength, which improves the reliability and life of the power module in terminal applications.

[0023] Furthermore, S100 includes:

[0024] S101, placing the lead frame and the DBC board into a plasma cleaning machine for cleaning;

[0025] S102, placing the cleaned lead frame and DBC board into a bonding fixture for fixing;

[0026] S103, replacing a bonding blade in an ultrasonic terminal bonding machine;

[0027] S104, setting and correcting the operating parameters of the ultrasonic terminal bonding machine according to the distribution position and pin parameters of each pin in the DBC board;

[0028] S105, bonding the pins on the lead frame to the DBC board using an ultrasonic bonding machine.

[0029] Beneficial effect: Put the lead frame and DBC board into the plasma cleaning machine for cleaning, which can clean the oxides and welding residues on the bonding surface of the DBC board and the lead frame, which is beneficial to improve the bonding strength, thereby making the bonding effect better; after cleaning, put it into the vacuum adsorption fixture in the bonding fixture, vacuum adsorb the DBC board, and realize the limit of the lead frame and DBC board; replace the bonding knife in the ultrasonic terminal bonding machine, set and calibrate the operating parameters of the ultrasonic terminal bonding machine according to the distribution position and electrode parameters of each electrode in the DBC board, which can ensure Ensure the accuracy and consistency of the bonding process, thereby improving the bonding quality of the product; use an ultrasonic bonding machine to bond the pins on the lead frame to the DBC board, and use the ultrasonic bonding machine to bond the lead frame and DBC board fixed by a bonding fixture. The ultrasonic bonding machine is equipped with a high-precision automatic control system that can quickly and accurately locate and bond thousands of pins, greatly improving production efficiency. The ultrasonic bonding machine can ensure that each bonding point is made under the same conditions, including parameters such as pressure, ultrasonic frequency and bonding time, thereby ensuring uniform bonding quality on the entire DBC board.

[0030] Further, in S104, the bonding frequency range of the ultrasonic terminal bonding machine is adjusted to be within a range of 20 kHz to 25 kHz, and the deformation amount range is within a range of 150 um to 240 um.

[0031] Beneficial effects: The lead frame and DBC board are bonded at a bonding frequency of 20kHz to 25kHz, and this frequency range is suitable for most thin metal wire bonding processes. In this frequency range, the transmission of ultrasonic energy is relatively stable, which can effectively activate the atoms on the surface of the material and promote the formation of solder joints; the deformation range is 150um to 240um, and the deformation within this range can ensure sufficient pin bonding strength without excessively deforming the pins and reducing the reliability of the overall structure; it is suitable for the manufacturing process of DPIM power semiconductor modules with small size and compact chip layout.

[0032] Bonding the lead frame and DBC board under a bonding frequency range of 20kHz to 25kHz and a deformation range of 150um to 240um can ensure the qualified rate of lead bonding, reduce the probability of false pressure, and avoid DBC board breakage due to excessive ultrasonic energy, thereby ensuring the bonding yield.

[0033] Further, in S200, a thrust tester is used to perform a push-pull force test on the bonded DBC board, the bonded DBC board is placed on the thrust tester, and a push-pull force perpendicular to the direction of the DBC board is applied to the pins by the thrust tester.

[0034] Beneficial effects: Through push-pull force tests, the mechanical strength of the bonding points can be accurately measured to ensure that each bonding point has sufficient strength to withstand various forces in subsequent processes and use. During the test, poorly bonded or defective bonding points often show force values ​​below the standard, which helps to promptly discover and eliminate defects in the production process. Parameters can be changed and adjusted based on the condition of the bonding surface to further reduce the damage rate, prevent defective products from entering the market, ensure that the power pins are fully bonded to the DBC board, and there is no virtual pressure, thereby improving the pass rate of the entire batch.

[0035] Further, in S300, the DBC plate is placed in a high negative ion environment for static electricity removal.

[0036] Beneficial effect: In a high negative ion environment, the negative ions generated by the ionization of the air move rapidly outward and combine with the positive charges on the DBC board to neutralize static electricity. The high negative ion environment can more comprehensively cover all parts of the DBC board without leaving any dead corners, thereby achieving a full range of static electricity removal effects. Specifically, the DBC board is placed in a high negative ion environment for 3 minutes of static electricity removal treatment. It should be noted that the static electricity treatment time is determined according to the area of ​​the DBC. The process of the present invention is suitable for small-volume DPIM power modules, that is, small DPIM power semiconductor modules with dimensions ranging from 27.9mm×24.1mm×6mm to 32.5mm×29.5mm×6mm.

[0037] Further, in S300, the surface of the DBC plate is purged with an inert gas.

[0038] Beneficial effects: The purging treatment can ensure that the bonding points between the aluminum wire and the chip and the DBC board are not contaminated, which is crucial to ensure the long-term stability and electrical performance of the bonding points. The surface of the DBC board is purged with an inert gas. Specifically, nitrogen can be used for purging, which can not only effectively remove surface pollutants, but also prevent oxidation of the DBC board surface during the treatment process, thereby ensuring product reliability.

[0039] Furthermore, S400 includes:

[0040] S401, mounting a number of chips and thermistors on the DBC board using an automatic chip mounter;

[0041] S402, placing the DBC board with the chip and thermistor mounted thereon into a vacuum soldering furnace for high temperature soldering.

[0042] Beneficial effects: Using an automatic chip mounter to mount several chips on the DBC board can quickly and accurately place the chips on the DBC board, can handle chips of various sizes and shapes, and can achieve high-efficiency and high-precision electronic component assembly; using an automatic chip mounter to mount thermistors not only improves the mounting efficiency, but also ensures their relative position with other chips through precise control, thereby achieving more reliable temperature monitoring; the vacuum environment of the vacuum welding furnace can effectively reduce the gas residue in the solder and avoid the formation of bubbles in the molten solder, thereby reducing welding voids. The voids will seriously affect the mechanical strength and conductivity of the solder joints, and vacuum welding can greatly reduce this risk.

[0043] Furthermore, in S400, a metal wire bonding machine is used to bond metal wires between the DBC board and each chip and between chips, and the metal wires are one of aluminum wires, copper wires and gold wires.

[0044] Beneficial effects: Metal wire bonding machines are usually highly automated and can quickly and accurately complete large-scale bonding operations, greatly improving production efficiency. Compared with manual wire bonding, automated equipment can provide more consistent and repeatable bonding quality; according to different application requirements, aluminum wire, copper wire or gold wire can be flexibly selected for bonding, and bonding process parameters can be adjusted to obtain the best bonding effect. This flexibility enables metal wire bonding technology to adapt to a variety of different application scenarios and performance requirements.

[0045] Furthermore, performing glue filling treatment on the chips and metal wires on the DBC board includes: placing the DBC board after bonding the metal wires in a glue filling fixture, and performing glue filling treatment on the chips and metal wires on the DBC board.

[0046] Beneficial effects: Placing the DBC board in a glue potting fixture for glue potting can realize automated operation and complete multiple steps at one time, which not only simplifies the production process, but also reduces the uncertainty and errors caused by manual operation, such as glue splashing, excessive glue, insufficient glue and other problems. Placing the DBC board after bonding the metal wire in a glue potting fixture for glue potting can not only enhance the mechanical protection and environmental adaptability of the product, but also optimize the heat dissipation performance, simplify the production process and improve the reliability of the product.

[0047] Furthermore, curing the DBC board after the glue filling treatment includes: placing the DBC board after the glue filling treatment in an environment of 85° C. to 125° C., and baking and curing for 30 minutes to 60 minutes.

[0048] Beneficial effect: By placing the DBC board after glue filling in a high temperature environment of 85℃ to 125℃, the curing speed of the potting glue can be significantly accelerated, thereby shortening the entire production cycle. Placing the DBC board after glue filling in an environment of 85℃ to 125℃ for baking and curing for 30 minutes to 60 minutes can not only accelerate the curing process and improve the performance of the potting glue, but also enhance the reliability and durability of the product and optimize the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 The present invention is a flowchart of a method for manufacturing a power semiconductor according to an embodiment of the present invention.

[0050] Figure 2 It is a schematic diagram of the local structure when the DBC board and the lead frame are bonded in the prior art.

[0051] Figure 3 It is a schematic diagram of the local structure when the DBC board and the lead frame are bonded in an embodiment of a power semiconductor manufacturing method of the present invention. DETAILED DESCRIPTION

[0052] The following is further described in detail through specific implementation methods:

[0053] The symbols in the drawings of the specification include: DBC board 1, lead frame 2, lead 3, bonding knife 4, bonding fixture 5.

[0054] In the description of this application, unless otherwise clearly specified and limited, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance; unless otherwise specified or explained, the term "plurality" refers to two or more; the terms "connected" and "fixed" should be understood in a broad sense, for example, "connected" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0055] In the description of this specification, it should be understood that the directional words such as "upper", "lower", "left", and "right" described in the embodiments of the present application are described at the angles shown in the accompanying drawings and should not be understood as limitations on the embodiments of the present application. In addition, in the context, it should also be understood that when it is mentioned that an element is connected to the "upper", "lower", "left", or "right" of another element, it can not only be directly connected to the "upper", "lower", "left", or "right" of another element, but can also be indirectly connected to the "upper", "lower", "left", or "right" of another element through an intermediate element.

[0056] Embodiment 1:

[0057] A method for manufacturing a power semiconductor, such as Figure 1 As shown, the following steps are included:

[0058] S100 , utilizing ultrasonic energy of an ultrasonic terminal bonding machine to bond a lead frame 2 onto a DBC board 1 ; the lead frame 2 is provided with a plurality of leads 3 .

[0059] In this embodiment, the DBC board 1 is a ceramic substrate; the DBC board 1 and the lead frame 2 are provided, and the DBC board 1 and the lead frame 2 are placed in a bonding fixture 5, the model of the bonding fixture 5 is DPIM-JH-8-Z0. In this embodiment, an ultrasonic bonding process is adopted and ultrasonic energy is used to bond the metal pins 3 on the lead frame 2 to the DBC board 1. The power bonding process does not require the use of additional flux or solder as an auxiliary material for electrical connection. Compared with the existing welding process (using a medium such as solder / welding strip / welding sheet to weld the pins and the DBC board 1 together using a vacuum welding furnace), when the terminal is welded, if the solder is inside and the flux cannot be well released, it will affect the welding strength. The present invention uses an ultrasonic bonding process to directly bond the copper terminal on the lead frame 2 to the DBC board 1 using ultrasonic energy, applies pressure and ultrasonic power to the bonding interface between the pin 3 and the DBC board 1 to achieve diffusion bonding, and uses ultrasonic energy to form a good ohmic contact on the connection surface to establish a reliable connection, so as to achieve a stable mechanical connection and electrical connection. Placing the pin 3 bonding process before the power chip welding avoids the influence of the stress generated by chip welding on the power pin 3 bonding area, thereby improving the product power pin 3 bonding yield. This improvement reduces the risk of pin 3 bonding failure caused by subsequent high-temperature processes, and can improve the production yield and electrical reliability of the product.

[0060] S100 includes:

[0061] S101, placing the lead frame 2 and the DBC board 1 in a plasma cleaning machine for cleaning for 2 to 5 minutes to clean the oxides or impurities on the surfaces of the DBC board 1 and the lead frame 2, which is beneficial to improving the bonding strength, thereby achieving a better bonding effect.

[0062] S102 , placing the cleaned lead frame 2 and DBC board 1 into a bonding fixture 5 for fixing; placing the lead frame 2 and DBC board 1 into the bonding fixture 5 for fixing, thereby fixing the lead frame 2 and DBC board 1 . In this embodiment, the bonding fixture 5 includes a vacuum adsorption fixture and a pressing fixture. The DBC board 1 is placed on the vacuum adsorption fixture at the bottom. The vacuum adsorption fixture adsorbs the DBC board 1 by generating negative pressure to fix it in a predetermined position to prevent displacement during the bonding process and facilitate the removal of the DBC board after the pin bonding is completed. The lead frame 2 and the DBC board 1 are placed in the bonding fixture 5, and it is ensured that the bonding surface of the lead frame 2 is in close contact with the bonding surface of the DBC board 1 to ensure good contact. On the one hand, it can provide better heat conduction and electrical connection, and on the other hand, it can guarantee the product and qualified rate under relevant parameters. If there is no tight fit, it is easy to cause the pre-set bonding energy to be insufficient, resulting in virtual pressure. Then, the lead frame 2 is pressed on the lead frame 2 using a pressing fixture. The pressing fixture ensures the firm connection between the lead frame 2 and the DBC board 1 through mechanical pressure, further eliminates the gap, and ensures the stability of the bonding process and the accuracy of relevant parameters. The use of the bonding fixture 5 can ensure the accurate positioning and firm fixation of the DBC board 1 and the lead frame 2, thereby providing a stable and reliable basis for terminal bonding.

[0063] S103, replace the bonding blade 4 in the ultrasonic terminal bonding machine; in this embodiment, the cross-sectional dimensions of the bonding surface of the terminal bonding blade 4 are specifically: 2520um in length and 2520um in width. The cross-sectional dimensions of the bonding surface of the terminal bonding blade 4 are 2520um in length and 2520um in width. This dimension determines the area of ​​the contact surface between the terminal bonding blade 4 and the bonding point. The terminal bonding blade 4 with a specification of 2520um×2520um is more suitable for small-volume modules, that is, small terminal bonding, and is suitable for bonding large electrodes and small electrodes of insulated gate bipolar transistor modules. The DBC board 1 of the insulated gate bipolar transistor module is not easily damaged or cracked.

[0064] S104, setting and correcting the operating parameters of the ultrasonic terminal bonding machine according to the distribution position and pin parameters of each pin 3 in the DBC board 1; setting and correcting the operating parameters of the ultrasonic terminal bonding machine according to the distribution position and pin parameters of each pin 3 in the DBC board 1 can ensure the accuracy and consistency of the bonding process, thereby improving the product bonding quality.

[0065] In S104, the bonding frequency range of the ultrasonic terminal bonding machine is adjusted to be within 20kHz to 25kHz; the lead frame and the DBC board are bonded at a bonding frequency of 20kHz to 25kHz, and this frequency range is suitable for the bonding process of most thin metal wires. Within this frequency range, the transmission of ultrasonic energy is relatively stable, which can effectively activate the atoms on the surface of the material and promote the formation of solder joints; the deformation range is 150um to 240um, and the deformation within this range can ensure sufficient pin bonding strength without causing excessive deformation of the pin and reducing the reliability of the overall structure; it is suitable for the manufacturing process of DPIM power semiconductor modules with small size and compact chip layout.

[0066] The deformation amount range is within 150um to 240um; the deformation amount refers to the degree of deformation of the bonding part of the power pin 3 caused by ultrasonic energy during the bonding process of the power pin 3; the bonding frequency range and the deformation amount range in this embodiment are based on product design requirements. When the original process is not suitable for the small-volume DPIM power module manufacturing process, after presetting a reasonable range, a range is selected within the range. Through sample verification, a parameter range that can achieve the best bonding effect is obtained, which is the parameter set by the ultrasonic terminal bonding machine.

[0067] In summary, bonding the lead frame 2 and the DBC board 1 when the bonding frequency ranges from 20kHz to 25kHz and the deformation ranges from 150um to 240um can ensure the qualified rate of the bonding of the lead 3, reduce the probability of false pressure, and avoid the DBC board 1 from breaking due to excessive ultrasonic energy, thereby ensuring the bonding yield.

[0068] S105, using an ultrasonic bonding machine to bond the pins 3 on the lead frame 2 to the DBC board 1. Using the ultrasonic energy of the ultrasonic terminal bonding machine of model SmartWelder SW1085, in this embodiment, the bonding head power range of the ultrasonic terminal bonding machine is within 400W to 1500W, the lead frame 2 is bonded to the DBC board 1, and the lead frame 2 and the DBC board 1 fixed by the bonding fixture 5 are bonded by the ultrasonic bonding machine. The ultrasonic bonding machine is equipped with a high-precision automatic control system, which can quickly and accurately locate and repeatedly bond the pins 3, greatly improving the production efficiency. The ultrasonic bonding machine can ensure that each bonding point is made under the same conditions, including parameters such as pressure, ultrasonic frequency and bonding time, so as to ensure uniform bonding quality on the entire DBC board 1.

[0069] In the present embodiment, the ultrasonic bonding process does not require the use of additional flux or solder as auxiliary materials. Compared with the existing process, the present invention utilizes ultrasonic energy to bond the metal pins 3 on the pin frame 2 to the DBC board 1, and applies pressure and ultrasonic power at the bonding interface between the pins 3 and the DBC board 1 to achieve diffusion bonding. Ultrasonic energy is utilized to form a good ohmic contact on the connection surface to establish a reliable connection, thereby achieving stable mechanical and electrical connections. Moreover, the actual bonding process only takes a few milliseconds to complete, thus avoiding the time cost of the traditional welding process, having high connection efficiency, and being suitable for automated mass production.

[0070] In this embodiment, these bonding interfaces usually need to have so-called "bumps" formed by chemical methods or wire bonding processes, which can reduce the contact area and compensate for tolerances. Diffusion bonding is achieved by applying pressure and ultrasonic power at the bonding cross section, and ultrasonic energy is used to promote the connection surface to form a good ohmic contact and establish a stable connection.

[0071] S200, push-pull force test is performed on the bonded DBC board 1; the connection strength is ensured by push-pull force test: push-pull force test is performed on the bonded DBC board 1 to ensure that each bonding point has sufficient mechanical strength to withstand various stresses in subsequent processes and use. This step helps to identify and eliminate potential poor bonding problems.

[0072] In S200, a thrust tester is used to perform a push-pull force test on the bonded DBC board. The bonded DBC board 1 is placed on the thrust tester. The model of the thrust tester is XYZTEC Condor. The thrust tester applies a push-pull force perpendicular to the direction of the DBC board 1 and away from the DBC board 1 upward to the pin 3. Specifically, the push-pull force applied by the push-pull force tester to the pin is perpendicular to the plane on the DBC board 1 where the pin is bonded, that is, under the condition of the three-axis operation of the thrust tester, the push-pull force test is performed from the Y-axis direction. The purpose of this is to detect the bonding condition of the pin 3. If a push-pull force is applied in the Y-axis direction, there are two situations. One is that the bonding force is not enough and the bonding force needs to be further increased; the other is that there may be a virtual pressure situation, that is, the applied bonding force is not enough. In either case, it proves that the product is unqualified. Through push-pull force tests, the mechanical strength of the bonding points can be accurately measured to ensure that each bonding point has sufficient strength to withstand various stresses in subsequent processes and use. During the test, poorly bonded or defective bonding points often show force values ​​below the standard, which helps to promptly discover and eliminate defects in the production process. Parameters can be changed and adjusted based on the condition of the bonding surface to further reduce the damage rate, prevent defective products from entering the market, ensure that the power pin 3 is fully bonded to the DBC board 1, and there is no virtual pressure, thereby improving the pass rate of the entire batch.

[0073] S300, performing a destaticizing and purging treatment on the DBC board 1 after the tensile test; performing a destaticizing and purging treatment on the DBC board 1 after the tensile test to eliminate static electricity accumulation and remove surface impurities, providing a clean, static-free surface for subsequent chip mounting, thereby improving the overall production quality; ensuring that the subsequent chip is not damaged by static electricity during welding and mounting, and at the same time, removing impurities remaining on the DBC board 1 during the bonding process to improve product reliability.

[0074] In S300, the DBC board 1 is placed in a high negative ion environment for static electricity removal. In a high negative ion environment, the negative ions generated by the ionization of the air move outward rapidly and combine with the positive charges on the DBC board to neutralize static electricity. The high negative ion environment can more comprehensively cover all parts of the DBC board without leaving any dead corners, and achieve a full range of static electricity removal effects. Specifically, the DBC board is placed in a high negative ion environment for 3 minutes of static electricity removal. It should be noted that the static electricity treatment time is determined according to the area of ​​the DBC. The process of the present invention is suitable for small-volume DPIM power modules, that is, small DPIM power semiconductor modules with dimensions of 27.9mm×24.1mm×6mm to 32.5mm×29.5mm×6mm.

[0075] In S300, an inert gas is used to purge the surface of the DBC board 1. The purging process can ensure that the bonding points between the aluminum wire, the chip and the DBC board 1 are not contaminated, which is crucial to ensure the long-term stability and electrical performance of the bonding points. The inert gas is used to purge the surface of the DBC board 1. In this embodiment, nitrogen is used to purge the DBC board 1, which can not only effectively remove surface contaminants, but also prevent oxidation of the surface of the DBC board 1 during the process.

[0076] S400, mounting a plurality of chips on the DBC board 1 after the static electricity removal and purging treatment, and bonding metal wires between the DBC board 1 and each chip to form an electrical connection between the DBC board 1 and the chip; in this embodiment, the chip is one or more of an IGBT chip, an FRD chip and a MOSFET chip, which can bring high efficiency, high reliability, excellent thermal management and electromagnetic compatibility, as well as wide application potential to power semiconductors; mounting a plurality of chips on the DBC board 1 after the static electricity removal and purging treatment, using the results of the previous steps to ensure that the chips can be mounted under the best conditions, thereby improving assembly efficiency and mounting accuracy.

[0077] S400 includes:

[0078] S401, using an automatic chip mounter to mount a number of chips and thermistors on a DBC board; using an automatic chip mounter to mount a number of chips on a DBC board 1, the chips can be placed on the DBC board 1 quickly and accurately, and can handle chips of various sizes and shapes, and can achieve high-efficiency and high-precision electronic component assembly; using an automatic chip mounter to mount thermistors on the DBC board 1; using an automatic chip mounter to mount thermistors not only improves the mounting efficiency, but also ensures its relative position with other chips through precise control, thereby achieving more reliable temperature monitoring.

[0079] S402, put the DBC board with the chip and thermistor mounted into a vacuum soldering furnace for high-temperature soldering. The vacuum environment of the vacuum soldering furnace can effectively reduce the residual gas in the solder and avoid the formation of bubbles in the molten solder, thereby reducing solder voids. Voids will seriously affect the mechanical strength and conductivity of the solder joints. Vacuum soldering can greatly reduce this risk. High-temperature soldering in a vacuum environment can enhance the bonding strength of the solder joints and improve long-term reliability.

[0080] In this embodiment, the automatic chip mounter is a power chip automatic chip mounter, the model is CPM FS-10, and other automatic chip mounters in the market can also be used. Automatic chip mounters often adopt modular design, and can flexibly match functions according to the production line process needs. For example, the equipment can be configured with different loading methods (such as wafer, tray or vibration plate loading), and is suitable for the placement of different types of materials, such as IGBT chips, solder pads, etc. The flexibility of this design greatly improves the application range and production efficiency of the equipment.

[0081] In S403, the DBC board 1 with the thermistor and several chips mounted thereon is placed in a vacuum welding furnace for high-temperature welding. The high-temperature welding is performed for 30 minutes in a vacuum environment at 220°C to 360°C so that the solder can melt, and the power chip is welded on the DBC board 1 to avoid welding voids that affect the module performance. Specifically, in a high-temperature environment at 220°C to 360°C, the solder can be fully melted, thereby ensuring that the welding layer between the chip and the DBC board 1 is uniform and void-free, which helps to improve the reliability and performance of the module. In addition, the overall assembly efficiency is also improved: welding the thermistor and the chip at one time can reduce the material stress caused by multiple heating, thereby improving the assembly efficiency and production pass rate of the entire power module.

[0082] In S400, metal wires are bonded between the DBC board 1 and each chip to form an electrical connection between the DBC board 1 and the chip. The bonding metal wires provide good electrical conductivity, ensuring that the current and signals between the chip and the DBC board 1 can be effectively transmitted. The connection points between the metal wires and the DBC board 1 and the chip have high mechanical strength and can withstand subsequent packaging processes and thermal cycle tests during use. Metal wires are bonded between the DBC board 1 and each chip to form a stable electrical connection, ensuring good electrical performance and long-term reliability. This step is the key to achieving efficient electrical interconnection.

[0083] In S400, a metal wire bonding machine is used to bond metal wires between the DBC board 1 and each chip, and the metal wire is one of aluminum wire, copper wire and gold wire. The model of the metal wire bonding machine is K&S ASTERION 7200PIUS, and other metal bonding machines on the market can also be used. Metal wire bonding machines usually have a high degree of automation capabilities and can quickly and accurately complete large-scale bonding operations, greatly improving production efficiency. Compared with manual bonding, automated equipment can provide more consistent and repeatable bonding quality; according to different application requirements, aluminum wire, copper wire or gold wire can be flexibly selected for bonding, and the bonding process parameters can be adjusted to obtain the best bonding effect. This flexibility enables metal wire bonding technology to adapt to a variety of different application scenarios and performance requirements. The present embodiment is preferably aluminum wire, which has a relatively high resistivity and a thermal expansion coefficient that is more compatible with most semiconductor materials, which can reduce the stress accumulation caused by temperature changes, thereby reducing the risk of failure caused by thermal stress.

[0084] S500, performing glue filling processing on the chip and the metal wire on the DBC board 1, and performing a curing processing on the DBC board 1 after the glue filling processing;

[0085] The curing treatment of the DBC board after the glue filling treatment includes: placing the DBC board 1 after the bonding metal wire is completed in a glue filling fixture, and performing glue filling treatment on the chip and metal wire on the DBC board 1. Specifically, placing the DBC board 1 in a glue filling fixture for glue filling treatment can realize automated operation and complete multiple steps at one time, which not only simplifies the production process, but also reduces the uncertainty and errors caused by manual operation. Placing the DBC board 1 after the bonding metal wire is completed in a glue filling fixture for glue filling treatment can not only enhance the mechanical protection and environmental adaptability of the product, but also optimize the heat dissipation performance, simplify the production process and improve the reliability of the product. Through the glue filling treatment, the product chip and internal metal wires are protected, which not only protects these sensitive components from the influence of the external environment, but also fixes their positions and cleans up the excess residual glue, which can protect these sensitive components from environmental factors such as humidity, temperature changes, mechanical shock and chemical corrosion, and improve the module performance. Based on the small-volume DPIM power module of our company targeted by the present invention, a glue potting fixture with model DPIM-GJ-13B-Z0 is used for glue potting and packaging, and the glue potting fixture disclosed in 2024218414284 can also be used for potting.

[0086] In S500, the DBC board 1 after the potting treatment is cured, and the potting glue is cured at high temperature to achieve the best physical properties, including higher insulation and vibration resistance.

[0087] The curing treatment of the DBC board after the glue filling treatment includes: placing the DBC board 1 after the glue filling treatment in an environment of 85°C to 125°C, and baking and curing for 30 minutes to 60 minutes. By placing the DBC board 1 after the glue filling treatment in a high temperature environment of 85°C to 125°C, the curing speed of the potting glue can be significantly accelerated, thereby shortening the entire production cycle. Placing the DBC board 1 after the glue filling treatment in an environment of 85°C to 125°C and baking and curing for 30 minutes to 60 minutes can not only accelerate the curing process and improve the performance of the potting glue, but also enhance the reliability and durability of the product and optimize the production process.

[0088] S600, the cured DBC board 1 is subjected to rib cutting, the pins 3 on the lead frame 2 are retained, and the connecting parts on the lead frame 2 are cut off. In this embodiment, the lead frame includes connecting parts and a plurality of pins, and the cut connecting parts include the electrode frame body, the pins, the bearing plate and the reinforcing ribs. After the pins 3 are bonded to the DBC board 1 using the lead frame 2, the product needs to be rib cut after the glue filling is completed, so that a single product can be separated from the lead frame 2. This step is particularly important for mass production, so that each individual component can be cut out quickly and accurately, which improves production efficiency and solves the problem that the single pin 3 welded by the clamp in the prior art cannot be mass-produced.

[0089] The products manufactured by the process steps of the prior art (Scheme 1) and the present scheme (Scheme 2) are compared respectively by thrust detection and eutectic area detection; the scheme of the prior art (Scheme 1) is as follows: an electrode welding method for an insulated gate bipolar transistor, comprising the following steps: S100, mounting a plurality of chips on a DBC board; S200, bonding aluminum wires between the DBC board and each chip to form an electrical connection between the DBC board and the chip; S300, bonding an electrode frame to the DBC board using ultrasonic energy of an ultrasonic terminal bonding machine; the electrode frame is provided with a plurality of electrodes and a plurality of pins; S400, performing glue filling treatment on the chip and aluminum wire on the DBC board; S500, performing rib cutting treatment on the DBC board after bonding the electrode frame, retaining the pins and electrodes on the electrode frame, and removing the connecting components on the electrode frame.

[0090] Table 1 below provides experimental comparison data of thrust testing and eutectic area effect testing of products manufactured by the prior art (Scheme 1) and the present scheme (Scheme 2), wherein the qualified range of thrust parameters for product thrust testing is 15Kg to 30Kg, and the qualified range of parameters for product eutectic area ratio is 60% to 90%.

[0091] Table 1 Experimental comparison data of thrust detection and eutectic area ratio detection

[0092]

[0093] As shown in Table 1 above, Scheme 1 is the prior art, and Scheme 2 is the present scheme. Compared with the prior art, the power semiconductor manufacturing method provided by the present scheme has a product produced by the pin bonding method. The individual values ​​of the eutectic area ratio of the electrical metal layer of the pin and the DBC ceramic substrate in each group are greater than those of the products manufactured by the prior art, and are all within the qualified range. However, the qualified rates of products manufactured by the prior art are uneven, and there are products with unqualified eutectic area ratios, which are not suitable for small-volume DPIM module products. The bonding contact between the pin and the electrical metal layer of the DBC ceramic substrate of the technical scheme of the present invention is more perfect, which improves the electrical performance of the final power module and is more suitable for the industrial production of small modules.

[0094] As shown in Table 1 above, the thrust detection comparison data of a power semiconductor manufacturing method of the present scheme and the prior art are provided. Among them, the products produced by the power semiconductor manufacturing method provided by the present scheme have the ultimate thrust that can be withstood after pin bonding, which is within the qualified range, while the qualified rates of products manufactured by the prior art are uneven, there are products that fail the thrust detection, and the product yield cannot be controlled. Furthermore, the bonding effect of the present scheme is better, the connection strength is higher, and the reliability and life of the power module in the terminal application are improved.

[0095] Under the same parameters of downward deformation, frequency, time, power and pressure detection parameters, the products manufactured by the process steps of the prior art (Scheme 1) and the present scheme (Scheme 2) are compared respectively. Table 2 below provides experimental comparison data of small-volume DPIM products with a volume size of 27.9 mm × 24.1 mm × 6 mm manufactured by the prior art (Scheme 1) and the present scheme (Scheme 2) under the above detection parameters. The table shows that the unqualified rate of products manufactured by the present scheme is 0, while there are unqualified products among the products manufactured by the prior art. The bonding effect of the present scheme is better and the connection strength is higher.

[0096] Table 2 Comparison of experimental parameters between Scheme 1 and Scheme 2

[0097]

[0098] like Figure 3 As shown, the power semiconductor module product manufactured by the method provided by the present invention is Figure 2 The prior art shown has better electrical performance and higher reliability. After adjusting the process, the present invention can ensure that the DBC ceramic substrate can be firmly fixed on the bonding fixture by vacuuming before bonding, and ensure that the DBC board does not shift during ultrasonic energy vibration, resulting in failure of the bonding pins. At the same time, the friction surfaces of the pins and the electrical metal layer of the DBC ceramic substrate are parallel, ensuring full contact between the pins and the electrical metal layer. During bonding, a larger eutectic surface can be formed between the two, reducing virtual pressure, improving the stability of the power module pins, and not easily falling off due to external factors, thereby improving the reliability of its terminal application.

[0099] The above are only embodiments of the present invention. Common knowledge such as the known specific structures and characteristics in the scheme is not described in detail here. Ordinary technicians in the relevant field know all the common technical knowledge in the technical field to which the invention belongs before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply conventional experimental means before that date. Ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for manufacturing a power semiconductor, characterized in that: The following steps are involved: S100, bonding a lead frame to a DBC board using ultrasonic energy of an ultrasonic terminal bonding machine; the lead frame is provided with a plurality of leads; S200, push and pull force test of DBC board; S300, performing static electricity removal and purging treatment on the DBC board; S400, mounting a plurality of chips on the DBC board, and bonding metal wires between the DBC board and each chip and between the chips to form electrical connections between the DBC board and the chips and between the chips; S500, performing glue filling processing on the chip and metal wire on the DBC board, and performing a curing processing on the DBC board after the glue filling processing; S600, perform rib cutting on the DBC board, retain the pins on the lead frame, and cut off the connecting parts on the lead frame.

2. The power semiconductor manufacturing method according to claim 1, characterized in that: S100 includes: S101, placing the lead frame and the DBC board into a plasma cleaning machine for cleaning; S102, placing the cleaned lead frame and DBC board into a bonding fixture for fixing; S103, replacing a bonding blade in an ultrasonic terminal bonding machine; S104, setting and correcting the operating parameters of the ultrasonic terminal bonding machine according to the distribution position and pin parameters of each pin in the DBC board; S105, bonding the pins on the lead frame to the DBC board using an ultrasonic bonding machine.

3. The power semiconductor manufacturing method according to claim 2, characterized in that: In S104, the bonding frequency range of the ultrasonic terminal bonding machine is adjusted to be within a range of 20 kHz to 25 kHz, and the deformation range is within a range of 150 um to 240 um.

4. The power semiconductor manufacturing method according to claim 1, characterized in that: In S200, a thrust tester is used to perform a push-pull force test on the bonded DBC board. The bonded DBC board is placed on the thrust tester, and a push-pull force perpendicular to the direction of the DBC board is applied to the pins by the thrust tester.

5. The power semiconductor manufacturing method according to claim 1, characterized in that: In S300, the DBC board is placed in a high negative ion environment for static electricity removal.

6. The power semiconductor manufacturing method according to claim 1, characterized in that: In S300, the surface of the DBC plate is purged with an inert gas.

7. The power semiconductor manufacturing method according to claim 1, characterized in that: S400 includes: S401, mounting a number of chips and thermistors on the DBC board using an automatic chip mounter; S402, placing the DBC board with the chip and thermistor mounted thereon into a vacuum soldering furnace for high temperature soldering.

8. The power semiconductor manufacturing method according to claim 1, characterized in that: In S400, a metal wire bonding machine is used to bond metal wires between the DBC board and each chip and between chips. The metal wire is one of aluminum wire, copper wire and gold wire.

9. The power semiconductor manufacturing method according to claim 1, characterized in that: The process of performing glue filling on the chip and metal wire on the DBC board includes: placing the DBC board after bonding the metal wire in a glue filling fixture, and performing glue filling on the chip and metal wire on the DBC board.

10. The power semiconductor manufacturing method according to claim 1, characterized in that: The curing treatment of the DBC board after the glue filling treatment includes: placing the DBC board after the glue filling treatment in an environment of 85° C. to 125° C., and baking and curing for 30 minutes to 60 minutes.

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